| Steve Buscemi | Enoch 'Nucky' Thompson |
| Kelly Macdonald | Margaret Thompson |
| Michael Shannon | Nelson Van Alden
(credit only) |
| Shea Whigham | Elias 'Eli' Thompson |
| Michael Stuhlbarg | Arnold Rothstein |
| Stephen Graham | Al Capone
(credit only) |
| Vincent Piazza | Lucky Luciano
(credit only) |
| Michael Kenneth Williams | Chalky White |
| Anthony Laciura | Eddie Kessler
(credit only) |
| Paul Sparks | Mickey Doyle |
| Jack Huston | Richard Harrow
(credit only) |
| Charlie Cox | Owen Sleater |
| Bobby Cannavale | Gyp Rosetti |
| Gretchen Mol | Gillian Darmody
(credit only) |
| Stephen Root | Gaston Means - Special Investigator |
| Erik LaRay Harvey | Dunn Purnsley |
| Meg Steedle | Lillian 'Billie' Kent
(as Meg Chambers Steedle) |
| Patrick Kennedy | Dr. Douglas Mason |
| Kerry O'Malley | Edwina Shearer |
| Glenn Fleshler | George Remus |
| Clea Alsip | Viola |
| Domenic Ambroselli | Dermot Thompson
(as Domenic Joseph Ambroselli) |
| Joseph Aniska | Agent Stan Sawicki |
| Chris Caldovino | Tonino Sandrelli |
| E.J. Carroll | Sheriff Victor Sickles |
| Kevin Csolak | William Thompson |
| Justiin A. Davis | Lester White
(as Justiin Davis) |
| Marc D. Donovan | Deputy Ramsey |
| Emily Dorsch | Cornelia Predock |
| Lo Freidenstine | Anne Thompson
(as Lola Freidenstine) |
| Josie Gallina | Emily Schroeder |
| Lucy Gallina | Emily Schroeder |
| Madeline Getty | Nora Thompson |
| Charles Gray | Switchblade Wielder at Bar |
| Mark Havlis | Sign Handyman
(as Mark Halvis) |
| Matt Hobby | House Servant Phillip |
| Emma Holzer | Edith Thompson |
| Christina Jackson | Maybelle Anne White |
| David Edward Jackson | Gas Jockey
(as David Jackson) |
| Robin Madel | Prudence |
| Jacqueline Pennewill | House Maid Lilian |
| Charlie Plummer | Michael Thompson |
| Grace Rex | Tabor Heights Diner Waitress |
| Ty Robinson | Samuel Crawford
(as Ty Michael Robinson) |
| Jonathon Ruckman | Mickey's Man |
| Nisi Sturgis | June Thompson |
| Nick Wyman | Dr. Landau |
| Brandon Zumsteg | Brian Thompson |
| Brian Harlan Brooks | Jazz Dancer #1 |
| Terrence Clowe | Jazz Dancer #2 |
| Cicily Daniels | Jazz Dancer #3 |
| Queen Esther | Jazz Dancer #4 |
| Francesca Harper | Jazz Dancer #5 |
| Dameka Hayes | Jazz Dancer #6 |
| James Jackson Jr. | Jazz Dancer #7 |
| Ernest Williams Jr. | Jazz Dancer #8 |
| Nick Diamantis | Rosetti Thug
(uncredited) |
| Risa Dorken | Lower Class Girl
(uncredited) |
| Logan Fry | Speakeasy Patron
(uncredited) |
| Michael Louis Gibson | Hirrum Cobb
(uncredited) |
| David Itchkawitz | Upscale Citizen
(uncredited) |
| Kellye Janel | Dancer
(uncredited) |
| Gregg Micheals | Salesman
(uncredited) |